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I. TOXICOLOGY

"All substances are poisons; there is none which is not a poison. The right dose differentiates a poison and a remedy."

Paracelsus

A. General Definitions

1) "Toxicology" is the study of the nature and action of poisons.

2) "Toxicity" is the ability of a chemical molecule or compound to produce injury once it reaches a susceptible site in or on the body.

3) "Toxicity hazard" is the probability that injury will occur considering the manner in which the substance is used.

B. Dose-Response Relationships

The potential toxicity inherent in a substance is manifest only when that substance comes in contact with a living biological system. A chemical normally thought of as "harmless" will evoke a toxic response if added to a biological system in sufficient amount. The toxic potency of a chemical is thus ultimately defined by the relationship between the dose (the amount) of the chemical and the response that is produced in a biological system.

C. Routes of Entry Into the Body

1) There are three main routes by which hazardous chemicals enter the body:

a) Absorption through the respiratory tract. Most important in terms of severity and most common route of exposure.

b) Absorption through the skin. Runs first in the production of occupational disease (such as dermatitis).

c) Absorption through the digestive tract. Can occur through eating with contaminated hands or in contaminated work areas.

2) Most exposure standards, Threshold Limit Values (TLVs) and Permissible Exposure Limits (PELs), are based on the inhalation route of exposure. They are normally expressed in terms of either parts per million (ppm) or milligrams per cubic meter (mg/m3) in air.

3) If a significant route of exposure for a substance is through skin contact, its MSDS will have a "skin" notation. Examples: pesticides, carbon disulfide, carbon tetrachloride, dioxane, mercury, thallium compounds, xylene, hydrogen cyanide, and benzene.

D. Exposure Definitions

1) Acute poisoning is characterized by rapid absorption of the substance and the exposure is sudden and severe. Normally, a single large exposure is involved. Examples: carbon monoxide or cyanide poisoning.

2) Chronic poisoning is characterized by prolonged or repeated exposures of a duration measured in days, months or years. Symptoms may not be immediately apparent. Examples: lead or mercury poisoning and pesticide exposure.

3) Local refers to the site of action of an agent and means the action takes place at the point or area of contact. The site may be skin, mucous membranes, the respiratory tract, gastrointestinal system, eyes, etc. Absorption does not necessarily occur. Examples: strong acids or alkalis.

4) Systemic refers to a site of action other than the point of contact and presupposes absorption has taken place. Examples: an inhaled material may act on the liver; arsenic affects the blood, nervous system, liver kidneys, and skin; benzene affects bone marrow.

5) Cumulative poisons are characterized by materials that tend to build up in the body as a result of chronic exposure. The effects are not seen until a critical body burden is reached. Example: heavy metals.

6) Synergistic ot potentiating effect occurs when two or more hazardous materials are present in combination. The resulting effect can be greater than the effect predicted based on the individual substances. Example: exposure to alcohol and chlorinated solvents.

E. Other Factors Affecting Toxicity

1) Rate of entry and route of exposure; that is, how fast the toxic dose is delivered and by what means.

2) Age, possibly affecting the capacity to repair tissue damage.

3) Previous exposure history, possibly leading to tolerance or increased sensitivity.

4) State of health, physical condition and lifestyle; pre-existing disease can result in increased sensitivity.

5) Environmental factors such as temperature and pressure.

6) Host factors including genetic predisposition and the sex of the exposed individual.

II. MATERIAL SAFETY DATA SHEETS (MSDS)

Definition and Policy

An chemical's MSDS provides the user with information on that particular chemical. The information is provided by the manufacturer or distributor of that chemical.

OSHA requires that the MSDS for each chemical used in the laboratory be accessible to every employee of that lab. MSDSs are available in hard copy, and a compilation of MSDSs are available online through CWRUnet. To access, type in our address: http://does.cwru.edu

Appendix B contains a sample MSDS, with all sections explained.

III. CLASSIFICATION OF TOXIC MATERIALS

A. Physical Classifications

1) A gas is a substance which exists in a gaseous state at room temperature and pressure.

2) A vapor is the gaseous phase of a material which is ordinarily a solid or a liquid at room temperature and pressure. When considering the toxicity of gases and vapors, the solubility of the substance is a key factor. Highly water-soluble materials like ammonia irritate the upper respiratory tract. On the other hand, relatively water-insoluble materials like nitrogen dioxide penetrate deep into the lung. Fat soluble materials, like pesticides, tend to have longer residence times in the body.

3) A liquid is the state of matter between a solid and a gas. Liquids present skin and ingestion hazards. A liquid can evaporate to the gaseous state and present a respiratory hazard.

4) An aerosol is composed of solid or liquid particles of microscopic size dispersed in a gaseous medium. The toxic potential of an aerosol is only partially described by its concentration in milligrams per cubic meter (mg/m3). For a proper assessment of the toxic hazard, the size of the aerosol's particles is important. Particles above 1 micrometer tend to deposit in the upper respiratory tract. Particles below 1 micrometer enter the lungs. Very small particles (<0.2 um) are generally not deposited.

B. Physiological Classifications

1) Respiratory

a) Mucous membranes may become inflamed by contact with certain chemical irritants. Inflammation of tissue results from concentrations far below those needed to cause corrosion. Examples of these irritants include: ammonia, alkaline dust and mist, arsenic trichloride, diethyl/dimethyl sulfate, hydrogen chloride, hydrogen fluoride, halogens, nitrogen dioxide, ozone, phosgene, and phosphorus chlorides.

Irritants can also cause changes in the mechanics of respiration and lung function. Examples include: acetic acid, acrolein, formaldehyde, formic acid, iodine, sulfuric acid, and sulfur dioxide

Long-term exposure to irritants can result in increased mucous secretions and chronic bronchitis.

• A primary irritant exerts no systemic toxic action either because the products formed on the tissue of the respiratory tract are non-toxic or because the irritant action is far in excess of any systemic toxic action. Example: hydrogen chloride.
• A secondary irritant's effect on mucous membranes is overshadowed by the systemic effect resulting from absorption. Exposure to a secondary irritant can result in pulmonary edema, hemorrhage and tissue necrosis. Examples include: hydrogen sulfide and aromatic hydrocarbons.

b) The central nervous system, especially the brain, may be depressed by anesthetics. Examples include: chloroform, diethyl ether, hexane and other nerve-depressing organic substances and alcohols. Many solvents also affect the central nervous system.

c) Asphyxiants have the ability to deprive tissue of oxygen. Simple asphyxiants are inert gases which displace oxygen. Examples include: carbon dioxide, hydrogen and helium, nitrogen, nitrous oxide. Chemical asphyxiants render the body incapable of utilizing an adequate oxygen supply. They can cause damage at very low concentrations. Examples include carbon monoxide and hydrogen cyanide.

d) Pulmonary agents damage the lungs. Examples include: asbestos, coal dust, cotton dust, silica, and wood dust. Dusts can cause a restrictive disease called pneumoconiosis. Other types of lung injuries include: edema, which can be caused by hydrogen fluoride, nickel carbonyl and perchlorethylene; and emphysema, which can be caused by ozone and oxides of nitrogen. Signs and symptoms: tightness in chest, shortness of breath.

2) Skin and Ingestion

a) Skin Toxins may result in anything from acute irritation to corrosion. Benzocaine, formaldehyde, and neomycin are all common chemicals which cause contact allergies. A sensitizer causes a substantial proportion of exposed people to develop an allergic reaction in normal tissue after repeated exposure to the chemical. The reaction may be as mild as a rash (contact dermatitis) or as serious as anaphylactic shock. Examples include: chlorinated hydrocarbons, chromium compounds, epoxies, nickel compounds, and toluene diisocyanate. Signs and symptoms include defatting of the skin, rashes, and irritation.

b) Eye toxins cause damage to the eye by direct contact, like any of the skin or mucous membrane toxins, or by systemic chemicals. The antimalarial drugs quinacrine and chloroquine have been shown to affect the cornea after oral administration. Signs and symptoms include conjunctivitis, and corneal damage.

3) Systemic

a) Hepatotoxic agents cause damage to the liver. Examples include: carbon tetrachloride, nitrosomines, and tetrachloroethane. Signs and symptoms include jaundice and liver enlargement.

b) Nephrotoxic agents damage the kidneys. Examples include: halogenated hydrocarbons and uranium compounds. Signs and symptoms include edema and proteinurea.

c) Neurotoxic agents damage the nervous system. The nervous system is especially sensitive to organo-metallic compounds and certain sulfide compounds. Examples include: carbon disulfide, manganese, methyl mercury, organo-phosphate insecticides, tetraethyl lead, thallium, and triakyl tin compounds. Signs and symptoms include narcosis, behavioral changes, decrease in motor function.

d) Hematotoxic agents act on the blood, bone marrow or hematopoietic system. Examples include: aniline, benzene, nitrites, nitrobenzene, and toluidine. Benzene damages bone marrow which can lead to leukemia. Signs and symptoms include cyanosis (a bluish coloration to the skin) and loss of consciousness.

e) A carcinogen commonly describes any agent that can initiate or speed the development of malignant or potentially malignant tumors or other malignant neoplastic proliferation of cells. Known human carcinogens are listed in Appendix C, subpart 1.

f) Reproductive toxins are chemicals which cause damage either to the reproductive system directly or to the fetal tissue. 1,2-Dibromo-3-chloropropane (DBCP) causes infertility (azoospermia) in males, while lead and ethylene oxide can cause infertility in males and females. Teratogens (embryotoxic or fetotoxic agents) interfere with normal embryonic development without damage to the mother or lethal effect on the fetus. Effects are not hereditary. Examples include: lead and 1,2-Dibromo-3-chloropropane (DBCP). See Appendix C, subpart 2, for a list of reproductive toxins. Signs and symptoms include sterility and birth defects.

g) Immune system effects, specifically immunosuppression, can be caused by a wide variety of chemicals, including arsenic, benzene, cadmium, lead, methyl mercury, nitrous oxide, and polycyclic aromatic hydrocarbons (PAHs).

h) The cardiovascular system may be damaged by exposure to a variety of chemicals. These chemicals may be cardiotoxic, i.e., causing damage to the heart directly, such as aliphatic alcohols, aldehydes and glycols, or they may cause damage to the vascular system. Heavy metals such as lead and cadmium fall into this latter category.

IV. WORKING SAFELY WITH HAZARDOUS CHEMICALS

It is the responsibility of the PI to determine the hazards associated with all of the chemicals used in his or her laboratory. There are many excellent compilations of the hazards associated with chemicals. The following references can be extremely useful and it is recommended that each unit have a least one of the following reference manuals available. All are available through University Libraries.

Suggested References on Hazardous Chemicals

Klaasen, C.D., Amdur, M, Doull, J., Cassarett and Doull's Toxicology: The Basic Science of Poisons, Third Edition, Macmillan Publishing Company, New York, New York, 1986

Lenga, R.A., The Sigma-Aldrich Library of Chemical Safety Data, Edition II, Volumes I and II, Sigma-Aldrich Corporation, 1988

Lewis, R.J. Sax's Dangerous Properties of Industrial Materials. 8th ed. 3 vols. New York: Van Nostrand Reinhold; 1996.

Lewis, R.J. Hazardous Chemicals Desk Reference. , New York: Van Nostrand Reinhold; 1997.

National Research Council. Prudent Practices for Handling Hazardous Chemicals in Laboratories. Washington DC: National Academy Press; 1981.

Perrin, D.D., Armarega, W.L.F., Perrin, D.R. Purification of Laboratory Chemicals. 4th ed. New York: Pergamon Press: 1996.

Raffle, P.A.B., Lee, W.R., McCallum, R , Murray, R., Hunter's Diseases of Occupations. 8th ed. London, Boston: E. Arnold; 1994.

See the Select Bibliography for additional references.

A. Hazardous Chemicals

The following is a list of types of hazardous chemicals, divided into eight general classes based on the predominant effects of those general chemical types.

1) Caustic or corrosive chemicals: These are acids or bases which may burn or otherwise damage human tissue on contact. The corrosion of equipment should also be considered. Examples include chromic acid cleaning solutions, concentrated acids such as hydrochloric, sulfuric, and nitric, and acid-releasing substances such as thienyl chloride and halogens (bromine, chlorine).

2) Poisons: The relative toxicity of this general class of chemicals is dependent on a large number of factors. This class would also include carcinogens. Examples include cyanide and azide salts.

3) Flammables: These are materials that will easily ignite, burn and serve as a fuel for a fire. Examples include most common laboratory organic solvents such as ether, acetone, tetrahydrofuran, and diethlyether.

4) Explosives: Chemicals in this class should be protected from shock, elevated temperatures, sparks, rapid temperature changes, and mixture with other reactive chemicals. Examples include nitroglycerin, nitrocellulose and organic peroxides.

5) Oxidizing and reducing chemicals: The reactions of oxidizing and reducing agents can generate heat and are often explosive. Oxidizing agents include oxygen, perchloric acid, and peroxyacids. Reducing agents include hydrogen, metallic hydrides, alkali metals, and activated zinc and phosphorus.

6) Water-sensitive chemicals: These chemicals react with water, steam and moisture in the air to evolve heat and/or flammable or explosive gases. Isolate water sensitive substances from other reactive chemicals and store in a cool, dry area. Examples of chemicals that liberate heat only are strong acids and bases, acid anhydrides and sulfides. Substances that liberate flammable gases are alkali metals, hydrides, nitrides, and anhydrous metallic salts.

7) Acid-sensitive chemicals: These chemicals react with acids to evolve heat, flammable and/or explosive gases and toxicants. Examples include alkali metals, cyanides, sulfides, carbonates, arsenic and related elements.

8) Pyrophoric agents: These chemicals burn when exposed to air. In general, they require absolute protection from air. Examples include phosphorus and activated zinc and nickel Raney catalyst.

B. Controlled Substances

Chemicals which are considered controlled substances are regulated by specific state and federal regulations. In order to purchase and distribute controlled substances (such as opiates, barbituates or anesthetics), appropriate State and Federal licenses must be obtained. If use of these classes of chemicals is required, contact Safety Services for information.

C. Chemical Safety

The potential dangers that may be encountered when working with hazardous chemicals are very diverse and depend greatly on the type of exposure. The dangers inherent in use of all chemicals in this manual are not completely described. It is the responsibility of the PI to be aware of potential hazards that exist when using the chemicals in his or her own laboratory. MSDSs are available for most specific chemicals and contain detailed information to inform workers about potential dangers of these materials.

V. WORKING SAFELY WITH EXTREMELY HAZARDOUS CHEMICALS: Select Carcinogens, Reproductive Hazards and Chemicals with a High Degree of Acute Toxicity

When working with certain hazardous chemicals the OSHA Lab Standard requires that you designate an area for such work. Chemicals for which special precautions are to be taken include carcinogens, including reproductive toxins, and certain chemicals with a high degree of acute toxicity.

A list of these substances is provided in Appendix C.

A. Creating A Designated Area

The designated area for use of extremely hazardous substances as defined by the standard may be a fume hood or a portion of the lab or the entire lab itself, depending on individual circumstances. The only requirements are that the area must be posted as to the nature of the hazard and that all employees who work in this area be informed as to the hazards involved. "Employees" include maintenance people who may be exposed to the hazard when working in the area.

In general, containment devices such as fume hoods or glove boxes are only required when using select hazardous substances that may become volatile, may result in the release of aerosols during manipulation, or may, through handling or reaction, result in the uncontrollable release of the substance. In addition, procedures for decontamination and the safe removal of contaminated waste must be outlined. The PI is strongly urged to seek the advice of Safety Services prior to experimentation with these substances.

1) General Procedures

a) All guidelines for safe laboratory practice--such as use of eye protection, wearing proper protective clothing, following correct pipetting procedures, wearing gloves, and not permitting smoking, eating and drinking in the laboratory--must be observed when working with extremely hazardous chemicals.

b) Laboratory clothing should be adequate to protect street clothing completely and should not be worn outside of the laboratory area. Disposable gloves should be discarded after each use and immediately after overt contact with extremely hazardous chemicals.

c) All personnel should wash their hands immediately after the completion of any procedure using chemical hazards.

2) Operational Procedures

a) Work areas within a laboratory should be clearly marked with a warning sign which reads: CAUTION-POTENTIAL CANCER HAZARD, AUTHORIZED PERSONNEL ONLY or CAUTION: POTENTIAL REPRODUCTIVE TOXIN-AUTHORIZED PERSONNEL ONLY. Those areas used for storage of these chemicals should also be identified in a similar manner.

b) Work areas where select hazards are being used should only be entered by authorized personnel. When extremely hazardous chemicals are being used in an area of a larger laboratory, the area should be clearly identified and should not be a high traffic area in order to minimize contact of uninvolved laboratory personnel with hazardous substances.

c) Work surfaces should be covered with impervious material such as dry absorbent plastic backed paper. The protective material should be decontaminated or disposed of after the procedures are completed. Adequate chemical traps must be used on all vacuum lines to prevent contamination of the vacuum systems. A separate vacuum pump should be used for extremely hazardous chemicals, and any service company should be informed of this use of the pump prior to service.

d) Procedures involving volatile chemicals or those which may result in the generation of aerosols or dispersible particulates should be conducted in a chemical fume hood. Work which may present a biological hazard should be conducted in a biological safety cabinet or glove box. Precautions should also be taken to prevent exposure to aerosols that may be generated during these procedures. Such equipment should be positioned so that any vapors or aerosols produced can be vented into a chemical fume hood. Aerosols can be generated from opening and closing vessels, transfer of chemicals (weighing chemicals), homogenization, open vessel centrifugation, and the application, injection or intubation of extremely hazardous chemicals to experimental animals. Minimum containment for tissue culture can be provided by a Class II, type B Biological Safety Cabinet. The PI should refer to the CDC/NIH publication Biosafety in Microbiological and Biomedical Laboratories, 3rd ed, USDHHS, 1996, for information concerning appropriate containment equipment and its usage. Check the CDC website for information on this manual (http://www. cdc.gov.od/ohs).

e) Stock and sample containers of extremely hazardous chemicals should be stored in a designated area that is clearly marked with the warning: CAUTION-POTENTIAL CANCER HAZARD or CAUTION-POTENTIAL REPRODUCTIVE HAZARD. The PI should maintain an inventory of each carcinogen or other select hazard. This inventory should include the quantities and the date purchased. The storage vessel should also be marked with a label indicating the specific potential danger of the substance. Working quantities should be kept to a minimum and should also have the same label.

f) If it is necessary to transfer the chemicals from one site to another, the chemical should be placed in a durable outer container. Contaminated materials should be placed in properly labeled biohazard bags to indicate the potential hazard. Safety Services should be contacted for the proper disposal of such material. Organic liquid waste should also be disposed of in containers per the chemical waste disposal guidelines by Safety Services, set forth in Chapter Four. In all cases, prior to initiating any experiments with select chemical hazards, the PI should make plans for the handling of chemical waste.

g) In order to ensure that the laboratory meets the standards for the use of a select chemical hazard (i.e., flow rate of the hood), the PI should contact Safety Services prior to initiating experiments.

B. Working With Select Carcinogens

"Select carcinogens" are defined by the OSHA Lab Standard as being any substance which meets one of the following criteria:

• It is regulated by OSHA as a carcinogen
• It is listed under the category "known to be carcinogens" in the Annual Report on Carcinogens published by the National Toxicology Program (NTP, latest edition)
• It is listed under Group 1, "carcinogenic to humans," by the International Agency for Research on Cancer Monographs (IARC, latest edition)
• It is listed in either Group 2A or 2B by IARC or under the category "reasonably anticipated to be carcinogens" by NTP. These chemicals cause statistically significant tumor incidence in experimental animals in accordance with any of the following criteria:
  • After inhalation exposure of 6-7 hours per day, 5 days per week, for a significant portion of a lifetime at dosages of less than 10 mg/m3
  • After repeated skin application of less than 300 mg/kg of body weight per week
  • After oral dosages of less than 50 mg/kg of body weight per day.

The most recent list which fulfills the first three of these criteria is in Appendix C, List of Extremely Hazardous Chemicals, Subpart 1, Carcinogens.

Additional information on the use of chemical carcinogens can be obtained from the U.S. Department of Health and Human Services by requesting "NIH Guidelines for the Laboratory Use of Chemical Carcinogens" and from Chemsyn Science Laboratories which will supply "Handling Chemical Carcinogens: A Safety Guide for the Laboratory Researcher" by Mary K. Dornhoffer. Check the MSDS to determine whether a particular chemical falls into this category.

C. Working With Reproductive hazards

Reproductive hazards are defined by the OSHA lab standard as:

"toxins (which) may manifest themselves in lethal effects on the fertilized egg, developing embryo or fetus or teratogenic (malformation) effects in the fetus. In addition, certain reproductive toxins may cause infertility in males and females."

Reproductive hazards include chemicals which target developing embryos and fetuses. Embryonic and fetal development is characterized by rapid growth and differentiation. In addition, maternal blood flow through the placenta increases and allows for fetal exposure to potential teratogens. Due to this unique sensitivity, any woman who believes she is pregnant should take special precautions to protect the developing fetus. If she chooses to declare her pregnancy, she should speak to her supervisor, informing him or her of her pregnancy, and they should then work together to develop ways to minimize her exposure to hazardous chemicals. The use of personal protective equipment or fume hoods may substantially reduce exposures and they are of particular significance for a pregnant employee. While no employee may be forced to abandon her job due to pregnancy, the PI should discuss any potential risks of exposure as soon as the fact of the pregnancy is known and assist the employee in developing programs to minimize exposure.

Examples of reproductive toxins include: benzene, mercury, ethylene dibromide, carbon monoxide, anesthetic gases (halothane) ionizing radiation, ethylene oxide, ethylene thiourea, and glycidyl ethers. A more complete list of known reproductive hazards is presented in Appendix C, Subpart 2, Reproductive Hazards. In addition, Material Safety Data Sheets may be consulted for information on additional chemicals with reproductive toxicity which may be in use in the laboratory. Safety Services is available at x2907 for consultation on both hazards and means of reducing exposures.

D. Working With Substances With High Acute Toxicity

The OSHA Lab Standard requires that "substances with high acute toxicity such as hydrogen cyanide, hydrogen sulfide and nitrogen dioxide are included under the category of substances for which employers must consider the need for special precautions. Such substances may be fatal or cause damage to target organs as a result of a single exposure or exposures of short duration."

E. Experimentation with Animals

The use of extremely hazardous chemicals in experimental animals should be arranged with the personnel in the Animal Resource Center. Call 368-3490 for information. Specific recommendations will be made by the Animal Research Committee on protocols to be used with chemical carcinogens.

VI. ULTRAVIOLET RADIATION EXPOSURE

A. Effects of Exposure

The eyes and skin should not be exposed to direct or strongly reflected ultraviolet radiation. The effect of radiation overexposure is dependent on such factors as dosage, wavelength, portion of body exposed and the sensitivity of the individual.

Overexposure of the eyes will result in a painful inflammation of the conjunctiva, cornea, and iris. Symptoms will develop 3 to 12 hours following exposure. There is a very unpleasant foreign body sensation accompanied by watery eyes . The symptoms usually disappear in a day or two.

Exposure to the skin will produce erythema (reddening) 1 to 8 hours following exposure.

B. Protection Against Ultraviolet Radiation Exposure

Adequate eye and skin protection must be worn when working in a UV irradiated area. Safety glasses designed specifically for use with UV light and with side shields or goggles with solid side pieces should be worn. The side pieces prevent the entrance of reflected radiation and direct radiation from a side source. Skin protection is afforded by face shields, caps, gloves, gowns, etc.

Overexposure to ultraviolet radiation should be reported to Health Services.

VII. BIOLOGICAL HAZARDS

Any person working with infectious agents should be familiar with the CDC/NIH manual "Biosafety in Microbiological and Biomedical Laboratories." See the CDC website for ordering information (http://www.cdc.gov/od/ohs).